2) Say you've written a pretty large program written mostly in proceduaral perl. Can you easily re-write that program in OO perl later if you choose to?

this would depend on how your code was structured originally. if you tend to code in a procedural language with an OO style, the conversion shouldn't be too hard. even most 'proper' procedural code shouldn't prove too difficult to convert if its all broken down cleanly.

3) Does anybody have any idea how perl 6's implementation of OO perl is going to be like? If so, is it going to be differnt from the current implementation?

Give "Perl 6 Essentials" a whirl ( O'Reilly, ISBN 0596004990) .. the content is nothing you can't find online already, but its nicely presented and will answer this and most any other question regarding how perl 6 is shaping up. in general, perl 6 is going to be more OO at the core ( moving several steps closer to languages like Ruby ) but whether or not you take advantage of the increased OOpiness will be up to you ( moving several steps closer to being the same perl we know ( and possibly love ) )